In this type of a molding machine, both injection unit and injection/stretch blow unit are installed on single bed. The injection/stretch blow unit is horizontally provided with a base platen on which installed are an injection mold clamping mechanism and a stretch blowing mechanism, the base platen being positioned above a lower base platen installed on a bed. As examples of such an upper base platen, there are known a movable one supported vertically movably by a hydraulic lift cylinder as is disclosed in Japanese Patent Laid-Open Publication No. 2004-122440 and a stationary one as is disclosed in Japanese Patent Publication No. Sho53 (1978)-22096. In both types, however, the space between both base platens is utilized as a work space, a transfer platen is attached to the underside of the upper base platen horizontally so as to be rotatable intermittently, the positions at which neck molds for a preform provided on a lower surface of the transfer platen stop in order are set as an injection molding operation section, a stretch blow molding operation section, and a product take-out operation section, respectively, and an injection mold clamping mechanism, a stretch blowing mechanism, and a take-out mechanism, are installed therein. As the case may be, the number of such stop positions is increased to add a temperature adjustment operation section.
In the injection mold clamping mechanism, which is a vertical type, tie bars erected on both sides of the injection molding operation section are inserted through the upper base platen and an overlying mold clamping platen to support them, a mold clamping cylinder block is fixed to upper ends of the tie bars, and mold clamping rams are connected to the mold clamping platen. Both ends of the upper base platen and the mold clamping platen are connected together through hydraulic opening/closing cylinders to make the mold clamping platen movable vertically with respect to the upper base platen, thereby permitting opening and closing core molds attached to a lower surface of the mold clamping platen.
In such an injection mold clamping mechanism, since the mold clamping cylinder block is fixed to the upper ends of the tie bars, the height of the mechanism is larger than that of the ordinary vertical type mold clamping mechanism, and in a certain workshop the molding machine cannot be carried into the interior. Moreover, since all of mold opening, closing and clamping works are performed by hydraulic means, the amount of oil used in hydraulic circuits is very large. Besides, since hydraulic cylinders are located higher than the upper base platen, there is a fear of contamination caused by oil leakage and thus there is the problem that the adoption of the injection mold clamping mechanism is difficult for some application of the resulting molded product.
Further, since both injection blow molding unit and injection unit are installed on a common bed, a mold change or maintenance work for the injection mold clamping mechanism must be done at an unstable attitude and requires much time.
Additionally, since the injection mold in the injection molding operation section and the blow mold in the stretch blow molding operation section are positioned in the work space below the upper base platen, the upper base platen and the underlying transfer platen are intervened between them and the injection mold clamping mechanism, as well as the stretch blowing mechanism, installed on the upper base platen. Therefore, mold closing between injection and blow cores positioned above the upper base platen and the injection and blow molds positioned below the upper base platen are performed by insertion of the cores though insertion holes formed in both upper base platen and transfer platen. Thus, mold clamping is performed in a state where the upper base platen and the transfer platen are sandwiched. As a result, there acts a stronger mold clamping force than in the ordinary case where molds are clamped to each other directly. In view of this point there has been proposed such a construction as is disclosed in Japanese Patent Laid-Open Publication No. 2004-262052 wherein an elongated hole permitting insertion therein of a core joint plate is formed to make direct mold clamping possible.
Anyhow, since the upper base platen above the work space exists, it is impossible to combine and superimpose injection core molds or blow cores beforehand onto neck molds and a mold as one set and then insert this set together with a mold assembly into the work space sideways of the machine base. According to the conventional method for avoiding such an inconvenience, installation of the mold assembly and attachment of neck molds to the lower surface of the transfer platen in the working space are performed firstly, the injection core molds or blow cores attached to a joint plate is inserted into the mold through holes from above the upper base platen secondly, and after temporary mold closing, the joint plate is secured to a mold clamping platen or a movable platen in the stretch blowing mechanism. Since the mold is divided into upper part and lower part interposing the upper base platen as a boundary, the assembling work takes time. It takes much time also for positioning the mold and the cores. Thus, there has been a problem on working efficiency in mold replacement.
Accordingly, it is an object of the present invention to provide an injection/stretch blow molding machine which adopts connecting means using a clamp to make it possible to clamp an injection mold and injection cores below a lower base platen, thereby reducing the height of an injection mold clamping mechanism and hence solving the problem of increase in height caused by a mold clamping cylinder block, and, by the adoption of an air cylinder, can prevent contamination of molded products caused by oil leakage and also can improve the molding efficiency by using a minimum amount of oil required.
It is another object of the present invention to provide an injection/stretch blow molding machine wherein a bed is divided into a bed for an injection mold clamping mechanism and a bed for an injection unit, thereby ensuring a work space for a mold replacement work, etc., and an injection unit can be installed regardless of screw length.
It is a further object of the present invention to provide a new injection/stretch blow molding machine wherein recesses are formed in edge sides of an upper base platen and of a transfer platen so that injection core molds or blow cores attached to a mold clamping block or a joint plate can be inserted into a work space in a superimposed state on a mold together with neck molds, thereby making it possible to perform the work for assembling both upper part and lower part of the base platen and hence possible to shorten the mold assembling time and positioning time.